Optical displays include laser scanned display fields. A period of rapid growth and change in the display industry has recently given rise to many new display technologies. W. Davis et. al. “MEMS-Based Pico Projector Display,” Proceedings of IEEE/LEOS Optical MEMS & Nanophotonics, Freiburg, Germany, (2008) discloses a unique application of micro electromechanical systems to the area of projection displays. Davis describes a representative example of a DMD-based projection display engine, the digital display engine. The digital display engine is based on a single-DMD device having array dimensions of 800600 elements, illuminated by a metal halide arc lamp through a compact optics train. The engine is designed for portable and fixed conference-room graphics and video display applications. Another example of a digital display engine is described in Lashmet et al, “A Single-Mirror Laser-Based Scanning Display Engine,” December 2008 Vol. 24, No. 12, Projection Displays Issue.
A problem with the prior-art laser scanning projection displays is that the farther the distance of the screen from the laser scan optics, the poorer the spatial resolution of the image due to the natural diffraction-based spreading of the Gaussian laser beam that forms the individual pixel/spot in the pixelated display.
Ideally, a laser scanning projection display that uses the lowest data overhead and produces the fastest frame rate with minimal power consumption would be advantageous. Laser scanning-based displays operate within a fixed image format produced by scanning a fixed N×M number of laser pixel spots on the screen. So regardless of the content of the image to be displayed, the laser scanning display physically scans all the N×M laser spots on the screen during. In addition, for grayscale control, the laser power is modulated to all N×M pixel positions. When N×M=1 million pixels, there is a high data overhead to operate the laser scanning display that requires laser beam motion via mirror scan options to one million angular space positions. As a result there is a tremendous hardware burden on the operational scan range and resolution of the scan mirror optics plus the control electronics for the laser and mirrors.
It is well known that typically images have some regions that are content rich while other regions in the image have a constant background. Compressive sensing is a new paradigm in imaging systems where one cleverly keeps the useful image data while discarding other image content as described in E. J. Candes et al., “Robust Uncertainty Principles: Exact Signal Reconstruction from Highly Incomplete Frequency Information,” IEEE Trans. Information Theory, Vol. 52, No. 2, February 2006; D. Donoho, “Compressed sensing,” IEEE Trans. Info. Theory, Vol. 52, No. 4, April 2006 and by R. G. Baraniuk, “Compressive Sensing,” IEEE Signal Proc. Mag., Vol. 118, July 2007.
In prior-art laser scanning displays, as the screen distance increases, the display pixel size gets larger due to beam diffraction and hence the image quality gets worse for larger screen distances and display image sizes. A compressive optical display was not possible with prior art displays because independent pixel size control was not possible given the fixed nature of the pixelated photo-sensor chip or the not-controllable laser beam spot size of prior-art laser scanning displays.
To solve the problems associated with the prior art laser scanning displays, the present invention provides a novel laser scanning-based optical display that operates as a compressive optical display by using the few custom compressed sensed image data pixels in the image space by electronically programming the laser spot beam to desired spot beam sizes, shapes, and locations. This results in a drastic reduction in number of individual scan spots results, thus increasing the display frame rate and reducing overall display power consumption.
The DMD is a powerful device not only for displays but also for realizing novel imaging methods as shown in the prior arts: S. Sumriddetchkajorn and N. A. Riza, “Micro-Electro-Mechanical System-Based Digitally Controlled Optical Beam Profiler,” Applied Optics-LP, Vol. 41, Issue 18, Page 3506 (June 2002); N. A. Riza, “Digital optical beam profiler,” U.S. Pat. No. 6,922,233, Jul. 26, 2005; Shree K. Nayar and Vlad Branzoi, “Programmable Imaging Towards a Flexible Camera,” International Journal of Computer Vision, Vol. 70, No. 1, pp. 7-22, 2006; Dharmpal Takhar, Jason N. Laska, Michael B. Wakin, Marco F. Duarte, Dror Baron, Shriram Sarvotham, Kevin F. Kelly, Richard G. Baraniuk, “A New Compressive Imaging Camera Architecture using Optical-Domain Compression,” Computational Imaging IV, edited by Charles A. Bouman, Eric L. Miller, Ilya Pollak, Proc. of SPIE-IS&T Electronic Imaging, SPIE Vol. 6065, 606509, 2006; Nabeel A. Riza, Syed Azer Reza and Philip J. Marraccini, “Digital Micro-Mirror Device-based Broadband Optical Image Sensor For Robust Imaging Applications,” Elsevier Optics Communications Journal, appeared on-line, Sep. 1, 2010; and N. A. Riza, “Agile optical image sensing, control, and measurement modules,” U.S. patent application Ser. No. 12/938,842 Filed Nov. 3, 2010, which is incorporation by reference. Here, the DMD is used with a maximum of two point detectors per wavelength band to acquire the incident optical irradiance pattern. Hence this imager can be considered a time sequential or serial design imager as one scans the entire image on a per pixel/point detector basis to acquire the full multi-pixel incident image. The method does provide high optical dynamic range but can be temporally slower and also have limited overall pixel count given the per DMD/CCD pixel or point-like data acquisition design.